Metal working – Method of mechanical manufacture – Assembling or joining
Patent
1990-04-13
1994-02-01
Rosenbaum, Mark
Metal working
Method of mechanical manufacture
Assembling or joining
29DIG11, 72349, 723794, 156224, 220604, 283 81, 283117, 355 52, 413 8, B21D 2220, B21D 3100, B21D 5126
Patent
active
052823067
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a draw-formed printed can and a process for the preparation thereof. More particularly, the present invention relates to a printed can obtained by draw-forming or draw-redraw-forming a preliminarily printed metal blank, in which formation of a striped pattern in the side wall portion of the can be prevented and further relates to an original print image can be faithfully reproduced, and a process for the preparation of this printed can.
Furthermore, the present invention relates to process in which formation of a printing plate from a printing original is carried out by a computer image processing. Moreover the present invention relates to a draw-formed printed can in which a print image having excellent linearity is displayed on the formed can without any error in due consideration of the anisotropy of the plastic flow of the metal blank, and a process for the preparation of this draw-formed printed can.
TECHNICAL BACKGROUND
Draw-forming of a surface-treated steel sheet such as a tinplate or tin-free steel sheet or a metal sheet such as an aluminum sheet is widely adopted for the manufacture of a so-called seamless can (two-piece can) and a metal cap. Coating or printing of individual formed bodies after the forming operation requires a complicated operation, and therefore, coating or printing of a flat blank before the draw-forming is desirable.
In draw-forming, a flat metal blank undergoes the plastic flow and is formed into a cup-shaped body. When the plastic flow of the portion of the flat blank, that will constitute the circumferential side wall portion of the formed body, is taken into consideration, it is confirmed that in this portion, elongation is caused in the direction corresponding to the height direction of the formed body.
In the preliminary printing of a flat blank for draw-forming, in view of the above-mentioned plastic flow of the blank, it is necessary that an original which is rectangular in the developed state should be converted to an annular printing plate. As means for effecting this conversion, there are known a hand-writing method, an optical conversion method and a digital conversion method proposed by us (Japanese Unexamined Patent Publication No. 61-267763 and Japanese Unexamined Patent Publication No. 61-267053).
However, in a can obtained by draw-forming a preliminarily printed metal blank, a striped pattern not found in the original print image is often formed at the upper part of the side wall portion, and this is especially conspicuous in a deep-draw-formed can or a can in which the thickness of the side wall portion is reduced by bending-rebending deformation.
As the result of the research made by us, it was found that in the draw forming of a preliminarily printed metal print, at the upper part of the side wall portion, dots become continuous owing to the compression flow of the blank in the circumferential direction and spaces between dots in the height direction increase owing to the elongation flow of the blank in the height direction, and this deformation of the dots tends to result in formation of a striped pattern.
Furthermore, the above-mentioned prior art techniques are defective in that the object is limited to an ordinary draw-formed can.
In the draw-redraw forming of a covered metal sheet, there is known a method in which the metal sheet is draw-formed into a deep-draw-formed cup by a curvature corner portion of a redrawing die and the side wall portion is subjected to the bending-rebending deformation to reduce the thickness. However, in the production of this thickness-reduced draw-formed can, there is not known a method in which the metal blank used is preliminarily printed and a print image faithful to the original image is manifested.
According to the above-mentioned hand-writing method, a rectangular transparent original ruled in squares is wound around the circumferential side wall portion of the draw-formed body, areas corresponding to the original image are painted by hand writing on the annular de
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patent: 3314329 (1967-04-01), Wolbert
patent: 4556312 (1985-12-01), Vany
patent: 4711611 (1987-12-01), Bachmann et al.
patent: 4935079 (1990-06-01), Nelson-Ashley et al.
patent: 4956906 (1990-09-01), Masse et al.
patent: 4962659 (1990-10-01), Imazu et al.
Ishinabe Masao
Katsuhiro Imazu
Kobayashi Tomomi
Machii Akihiko
Hughes S. Thomas
Rosenbaum Mark
Toyo Seikan Kaisha Ltd.
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